理想磁流体方程的MUSCL-型熵相容格式研究

针对磁流体动力学方程,本文提出了一种基于MUSCL-Hancock方法求解MHD方程的熵相容格式(EC-MHM格式),获得了一种求解理想磁流体动力学方程的高分辨率熵相容格式。该格式在解的光滑区域具有高精度;在解的间断区域可以合理地控制耗散,使抹平现象得到改善,还可有效避免非物理现象的产生。文中还证明了熵相容格式的收敛性。采用熵稳定格式、熵相容格式和新的高分辨率熵相容格式对理想磁流体动力学方程进行数值模拟。结果表明:新格式能准确地捕捉解的结构,且具有无振荡、高分辨、鲁棒等特性。Focusing on the idea magnetohydrodynamic (MHD) equations, this paper presents an entropy-consistent scheme based on the MUSCL-Hancock method for solving MHD equations, termed the Entropy Consistent MUSCL-Hancock (EC-MHM) scheme, and thus achieving a high-resolution entropy-consistent formulation for solving ideal MHD equations. This scheme exhibits high accuracy in smooth regions of the solution and effectively controls dissipation in discontinuous zones, leading to an improvement in the smearing phenomenon and efficiently preventing the emergence of non-physical oscillations. The convergence of the entropy consistent scheme is also proved. The ideal MHD equations are numerically simulated by entropy stable scheme, entropy consistent scheme and the new high resolution entropy consistent scheme. The results show that the new scheme can accurately capture the structure of the solution, and has the characteristics of no oscillation, high resolution and robustness.

干燥及冷冻处理对襄荷花苞挥发性成分的影响

目的:比较襄荷花苞在干燥及冷冻前后挥发性成分的差异。方法:采用顶空固相微萃取—气质联用法(HS-SPME-GC-MS)测定干燥及冷冻后襄荷花苞的挥发性成分,并通过峰面积归一化法计算其相对含量。结果:干燥及冷冻处理对襄荷花苞的挥发性成分影响显著(P<0.05),在新鲜、干燥和冷冻襄荷花苞中共鉴定出152种挥发性成分,含有多种挥发性药效成分,主要以烯烃类为主,其中β-水芹烯、α-律草烯和左旋-β-蒎烯相对含量较高。干燥及冷冻后襄荷花苞整体挥发性成分数量均明显减少,新鲜和冷冻样品中烯烃类相对含量较高,干燥后烯烃类和醇类相对含量较高。干燥及冷冻处理后有25种挥发性成分得以保留,同时出现了新的挥发性成分,赋予干燥和冷冻襄荷花苞独特风味。结论:新鲜、干燥和冷冻的襄荷花苞中含有较多的生理活性成分,干燥处理相较于冷冻处理对襄荷花苞挥发性成分的相对含量和组成影响更大,实际生产中根据应用目的选择合适的处理条件。